1. Field of Invention
The present invention relates to an ignition timing controller for an internal combustion engine.
2. Description of Related Art
An existing ignition timing controller for an internal combustion engine advances the ignition timing to a level at which knock does not occur, calculates an indicator that shows the knock resistance of a fuel, and interpolates a knock-limit ignition timing when regular gasoline is used and a knock-limit ignition timing when high octane gasoline is used, which have been stored beforehand, by using the indicator of the knock resistance.
However, with the existing ignition timing controller for an internal combustion engine, it is impossible to distinguish, from data of the knock-limit ignition timing alone, whether the knock resistance has increased and the ignition timing has been advanced due to the difference in the octane number of a fuel or due to a high ambient humidity. Therefore, there is a problem in that, in the case where the ignition timing has been advanced because the ambient humidity is high, the interpolated knock-limit ignition timing may be deviated from the actual knock-limit ignition timing.
An object of the present invention, which has been achieved in view of such a problem, is to calculate the knock-limit ignition timing accurately.